Mapping Thermophysical Diversity in Asteroid Families via Spin-Orbit V-Shape Morphology

Abstract: The dynamical evolution of asteroid families, primarily driven by the Yarkovsky effect, is often characterized by a V-shape morphology in size-semimajor axis space. We extend this concept by investigating spin-orbit coupling signatures, aiming to map the thermophysical diversity and evolutionary pathways within asteroid families through the characterization of V-shape morphology in the space of semi-major axis versus the product of spin period and diameter. Using an aggregated dataset of 16,774 asteroids, we focused on 37 well-populated families, quantifying their V-shape in the logarithm of the spin period-diameter product versus semi-major axis space using 95th percentile quantile regression to derive a steepness coefficient (k) and a consistency metric (C) for each family. Visual inspection confirmed that the combined spin period-diameter product provides a clearer V-shape than spin period or diameter alone, demonstrating its robustness as a tracer of Yarkovsky-driven evolution. Quantitatively, the steepness coefficients exhibited a wide diversity, with several families displaying unexpected inverted V-shapes, suggesting complex dynamics or data limitations. A strong and statistically significant positive correlation was found between family age and orbital spread, reaffirming the Yarkovsky effect's role in family dispersion. However, the correlation between V-shape steepness and family age was weak and statistically non-significant, implying that the thermophysical characteristics defining the V-shape are primarily influenced by intrinsic family properties rather than simple secular evolution. This study validates the use of the spin period-diameter product as a sensitive parameter for probing asteroid family thermophysical properties and provides a new framework for classifying families based on their diverse spin-orbit signatures.

Subjects:	astro-ph.EP; physics.space-ph
Cite as:	PX:2508.00058